Generally, when an electrical tool operates, an object to be processed usually needs to be clamped. As far as most electrical tools such as a mitre saw and a desktop saw are concerned, they usually employ a horizontal worktable. In order to clamp the object to be processed, typically a corresponding quick clamping device is provided on the worktable. The current quick clamping devices comprise clamping devices for locking in a threaded form, but they need to be rotated over and over during operation so that the operation is quite inconvenient and liable to cause fatigue. As an improvement, a quick clamping mechanism using principles of a lever or cam appears in the market. However, whatever mode is employed, an acting direction by a user's manual operation is often inconsistent with an actual clamping feeding direction. Therefore, the two kinds of quick clamping devices are relatively complex in structure and generally require complicated operation.